linux-kernel - Re: [PATCH 5/5] selftest/seccomp: add a new test for the sync mode of seccomp_user

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Message-ID: <B33DF09C-9121-4342-926E-B7B1988036B9@kernel.org>
Date:   Wed, 19 Oct 2022 22:04:44 -0700
From:   Kees Cook <kees@...nel.org>
To:     Andrei Vagin <avagin@...il.com>, linux-kernel@...r.kernel.org
CC:     Andy Lutomirski <luto@...capital.net>,
        Christian Brauner <brauner@...nel.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Kees Cook <keescook@...omium.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Peter Oskolkov <posk@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tycho Andersen <tycho@...ho.pizza>,
        Will Drewry <wad@...omium.org>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH 5/5] selftest/seccomp: add a new test for the sync mode of seccomp_user_notify

On October 19, 2022 6:10:48 PM PDT, Andrei Vagin <avagin@...il.com> wrote:
>Test output:
>RUN           global.user_notification_sync ...
>seccomp_bpf.c:4279:user_notification_sync:basic: 8655 nsec/syscall
>seccomp_bpf.c:4279:user_notification_sync:sync:	 2919 nsec/syscall
>OK  global.user_notification_sync

This looks like a benchmark, not a functionality test. But maybe the test is "is sync faster than async?"

>
>Signed-off-by: Andrei Vagin <avagin@...il.com>
>---
> tools/testing/selftests/seccomp/seccomp_bpf.c | 80 +++++++++++++++++++
> 1 file changed, 80 insertions(+)
>
>diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
>index 4ae6c8991307..01f872415c17 100644
>--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
>+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
>@@ -4241,6 +4241,86 @@ TEST(user_notification_addfd_rlimit)
> 	close(memfd);
> }
> 
>+/* USER_NOTIF_BENCH_TIMEOUT is 100 miliseconds. */
>+#define USER_NOTIF_BENCH_TIMEOUT  100000000ULL
>+#define NSECS_PER_SEC            1000000000ULL
>+
>+#ifndef SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP
>+#define SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP (1UL << 0)
>+#define SECCOMP_IOCTL_NOTIF_SET_FLAGS  SECCOMP_IOW(4, __u64)
>+#endif
>+
>+static void user_notification_sync_loop(struct __test_metadata *_metadata,
>+					char *test_name, int listener)
>+{
>+	struct timespec ts;
>+	uint64_t start, end, nr;
>+	struct seccomp_notif req = {};
>+	struct seccomp_notif_resp resp = {};
>+
>+	clock_gettime(CLOCK_MONOTONIC, &ts);
>+	start = ts.tv_nsec + ts.tv_sec * NSECS_PER_SEC;
>+	for (end = start, nr = 0; end - start < USER_NOTIF_BENCH_TIMEOUT; nr++) {
>+		memset(&req, 0, sizeof(req));
>+		req.pid = 0;
>+		EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0);
>+
>+		EXPECT_EQ(req.data.nr,  __NR_getppid);
>+
>+		resp.id = req.id;
>+		resp.error = 0;
>+		resp.val = USER_NOTIF_MAGIC;
>+		resp.flags = 0;
>+		EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0);

I think these EXPECTs should be ASSERTs...

>+
>+		clock_gettime(CLOCK_MONOTONIC, &ts);
>+		end = ts.tv_nsec + ts.tv_sec * NSECS_PER_SEC;
>+	}
>+	TH_LOG("%s:\t%lld nsec/syscall", test_name, USER_NOTIF_BENCH_TIMEOUT / nr);
>+}
>+
>+TEST(user_notification_sync)
>+{
>+	pid_t pid;
>+	long ret;
>+	int status, listener;
>+
>+	ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
>+	ASSERT_EQ(0, ret) {
>+		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
>+	}
>+
>+	listener = user_notif_syscall(__NR_getppid,
>+				      SECCOMP_FILTER_FLAG_NEW_LISTENER);
>+	ASSERT_GE(listener, 0);
>+
>+	pid = fork();
>+	ASSERT_GE(pid, 0);
>+
>+	if (pid == 0) {
>+		while (1) {
>+			ret = syscall(__NR_getppid);
>+			if (ret == USER_NOTIF_MAGIC)
>+				continue;
>+			break;
>+		}
>+		_exit(1);
>+	}
>+
>+	user_notification_sync_loop(_metadata, "basic", listener);
>+
>+	EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SET_FLAGS,
>+			SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP, 0), 0);

Same here.

Also can you test that invalid SET_FLAGS are correctly rejected here?

>+
>+	user_notification_sync_loop(_metadata, "sync", listener);
>+

If the timings are collected, add a test that sync is <= async here?

>+	kill(pid, SIGKILL);
>+	EXPECT_EQ(waitpid(pid, &status, 0), pid);
>+	EXPECT_EQ(true, WIFSIGNALED(status));
>+	EXPECT_EQ(SIGKILL, WTERMSIG(status));
>+}
>+
>+
> /* Make sure PTRACE_O_SUSPEND_SECCOMP requires CAP_SYS_ADMIN. */
> FIXTURE(O_SUSPEND_SECCOMP) {
> 	pid_t pid;

Otherwise, yeah, looks good.


-- 
Kees Cook